1. Field of the Invention
The present invention relates to an identification indication reading apparatus for reading an identification indication such as a bar code provided on an optical disc and a method therefor.
2. Description of the Prior Art
There are known optical discs which are provided with an identification indication such as a bar code or the like to identify various information. For example, in the case of an optical disc 3 such as a photo CD developed by Kodak, Inc., as shown in FIG. 1, an arc-shaped bar code 3d is provided on an annular bar code area 3c formed between a clamping area 3b and a program area 3e of the optical disc 3. With this bar code 3d, various information such as the disc manufacturer and the date of manufacturing is specified, thereby enabling to determine the type of disc, the disc format and the like. In order to read the bar code of an optical disc such as the photo CD, a photo-interrupter for reading bar code information must be provided in addition to an optical pick-up for reading data recorded in the program area 3e of the optical disc.
In this connection, FIG. 2 shows an example of a disc drive which includes such a photo-interrupter (Japanese Laid-Open Patent Application HEI 7-182659). As shown in this drawing, in this disc drive a photo-interrupter 9a is mounted on a sensor platform 9 which is provided in the vicinity of a turntable 8. Thus, by means of the photo-interrupter 9a, the bar code of the loaded optical disc is read out from the lower side of the optical disc. In this way, in the disc drives of the prior art, the photo-interrupter 9a is positioned underneath the optical disc, namely, the photo-interrupter 9a is positioned at the side where the optical pick-up and the turntable 8 are provided, and the bar code is read from underneath the loaded optical disc.
In the meantime, a disc drive having an identification indication reading apparatus is proposed in Japanese patent application filed by the present inventor on Sep. 26, 1997 (Japanese Patent Application No. HEI 8-275469)). In the disc drive, a photo-interrupter is mounted on a disc clamper supporting member to read a bar code provide on an optical disc from the upper side of the loaded optical disc.
However, because letters, marks, patterns and the like are printed on the upper surface of the optical disc, when the bar code provided on the optical disc is read from the upper side of the optical disc, such letters, marks, patterns and the like are liable to become a source of noise. Further, scratches, dust or the like on the upper surface of the disc are also likely to become a source of noise. In this connection, this problem of noise caused by scratches, dust or the like is not limited to the case where the bar code of the optical disc is being read from the upper side of the optical disc. Such a problem also occurs in the case where the bar code of the optical disc is read from the underside of the optical disc. When this kind of noise occurs, there is a case where such noise is confused with a signal from the bar code, thereby making it impossible to accurately read the bar code of the optical disc.